
<!DOCTYPE html>
<html lang="en">
    <head>
        <meta charset="UTF-8">
        <meta name="viewport" content="width=device-width, initial-scale=1.0">
        <meta http-equiv="X-UA-Compatible" content="ie=edge">
        <title>Document</title>
        <style>
            *{
                margin: 0px;
                padding: 0px;
                list-style: none;
            }
            div{
                width: 520px;
                height: 280px;
                margin:0px auto;
                position: relative;
                overflow: hidden;
            }
            ul{
                width: 9999px;
                position: relative;
                left:0px
            }
            ul li{
                float: left;
            }
            ul img{
                width: 520px;
                height: 280px;
            }
            ol{
                position: absolute;
                bottom:0px;
                left:50%;
                transform: translateX(-50%);
            }
            ol li{
                margin:0px 4px;
                width:10px;
                height: 10px;
                border-radius: 50%;
                background:white;
                float: left; 
                cursor: pointer;
            }
            span{
                position: absolute;
                top:50%;
                transform: translateY(-50%);
                background:skyblue;
                cursor: pointer;
            }
            .left{
                left:10px;
            }
            .right{
                right: 10px;
            }
            .current{
                background: #f60;
            }
        </style>
    </head>
    <body>
        <div id="wrap">
            <ul id="box">
                <li><img src="images/1.jpg" alt=""></li>
                <li><img src="images/2.jpg" alt=""></li>
                <li><img src="images/3.jpg" alt=""></li>
                <li><img src="images/4.jpg" alt=""></li>
            </ul>
            <ol id="list">
                <li class="current"></li>
                <li></li>
                <li></li>
                <li></li>
            </ol>
            <span class="left" id="left">左</span>
            <span class="right" id="right">右</span>
            <script>
                var num=0;
                var box=document.getElementById('box');
                var wrap=document.getElementById('wrap');
                var left=document.getElementById('left');
                var right=document.getElementById('right');
                var list=document.getElementById('list').children;
                var timer;
                function fn(){
                    timer=setInterval(function(){
                        num--;
                        if(num<-3){
                            num=0
                        }
                        for(var i=0;i<list.length;i++){
                            list[i].className='';
                        }
                        list[-num].className='current';
                        box.style.left=520*num+'px';

                    },1000)
                }
                fn()
                wrap.onmouseenter=function(){
                    clearInterval(timer)
                }
                wrap.onmouseleave=function(){
                    fn()
                }
                for(var i=0;i<list.length;i++){
                    list[i].index=i;
                    list[i].onclick=function(){
                        for(var n=0;n<list.length;n++){
                            list[n].className=''
                        }
                        this.className='current';
                        var m=this.index;
                        num=-m;
                        box.style.left=520*num+'px';

                    }
                }
                right.onclick=function(){
                        num--;
                        if(num<-3){
                            num=0
                        }
                        for(var i=0;i<list.length;i++){
                            list[i].className='';
                        }
                        list[-num].className='current';
                        box.style.left=520*num+'px'; 
                }
                left.onclick=function(){
                        num++;
                        if(num>0){
                            num=-3
                        }
                        for(var i=0;i<list.length;i++){
                            list[i].className='';
                        }
                        list[-num].className='current';
                        box.style.left=520*num+'px'; 
                }
            </script>
        </div>
    </body>
</html>